one perspective: Realistically, we have no idea what they're actually worth, as there's been a reluctance to consider the business model within this industry.
another: Actually, it's been considered and studied, but the academics who do so mainly talk to each other and mainstream media doesn't pick up on their studies because they aren't sensational.

Some sailing enthusiasts spend $100k/year on a boat they use only very occasionally. Do gamers like this exist? Are people willing to pay this much for electronic entertainment that doesn't take up a significant portion of their time?

Why do games have value for gamers?

Entertainment (of measurable quantity/quality)

Social interaction

The joy of winning

Status (achieved by winning, or gifting, or whatever is promoted by the game mechanic)

Learning

Exercise (Wii Fit or even Nike's in-shoe pedometer with leaderboard)

Unique experiences (like an expensive vacation or wine, it might not matter if you actually ENJOY the time spent)

Sex (Second Life?)

Academic interest (connoisseurs, other developers)

Book recommendation: A Theory of Fun, which says that all games teach something whether it's useful or not.
Human truths make good games? Mazlov's theories lead to The Sims, Darwin's lead to Spore.

The free-to-play, buy-your-items model:

Maple Story in China and Korea

Second Life

rationale: if we figure that players will use real money to conduct in-game business, why not facilitate it and take a cut? Provides security to the player and makes a tidy profit.

The Evil Genius model, ZT Online:

Buy prize boxes, which may have level-granting contents or not - if they do, player gains status in one of 9 warring kingdoms

Player goal is to achieve dominance of a kingdom, and must constantly grow to stay competitive

Through metrics, predictions are made of how much players are willing to spend - developer can initiate wars between kingdoms to spur increased prize box sales

Small rewards offered to losing players to offset emotional costs of losing (like a casino, free drink or room makes you forget the money you just threw away)

Large in-game (but free to the developer) rewards for winning can justify financial investment on player's part - if you kill a king in ZTO, a big announcement with your name on it goes out to everyone in the game.

Manage victory conditions so everyone feels like a winner somehow, even when they lose - "The other kingdom outspent us to death but we held them off for 45 minutes when they said it'd only take 10! We're the REAL winners!"